The present invention relates generally to an apparatus and method for purifying air, and, more particularly, to an apparatus and method for removing particles of a specified size from an air flow by attracting such particles to charged spray droplets of a fluid introduced to the air flow.
Indoor air includes many small particles which, when inhaled or otherwise contacted by human beings, have a pernicious effect. Dust alone comprises dead skin, dust mite feces, pet dander, and other microscopic (less than 10 microns in size) particles which elicit a human immune response. This is exemplified by dust mite feces, which comprise a wide array of serine and cysteine protease enzymes that cause respiratory irritation and are responsible for many allergy symptoms.
While filtration systems have been used to reduce the amount of small particles present in selected locations, many of the most commonly irritating materials still exist as particles within a range of about 0.1 micron to about 10 microns in size. Filters having pore openings small enough to be effective at removing particles in this size range are known to become easily occluded and generate high backpressure, thereby requiring high power air blowers. Moreover, the ability to maintain proper air conduction through such filters requires a significant amount of electrical energy, is expensive and cumbersome.
Other types of air purifying devices, such as ionic and electrostatic devices, utilize the charge on particles to attract them to a specified collecting surface which is charged at an opposite polarity. Such devices require the collecting surface to be cleaned constantly and have met with limited success in terms of efficiency.
It will be appreciated that small particles can collect in the home and be rebreathed by the occupants without the benefit of elaborate and high power consumption filtration systems found in the public domain. One vestige of prior art systems is their size and high electrical power demand, which affects the cost of operation and the aesthetics of a sizable filtration apparatus.
Accordingly, it is desirable that an apparatus and method of purifying air be developed which is capable of removing particles of a specified size (about 0.1 micro to about 10 microns) in a manner which is adaptable, non-intrusive, and ergonomically compatible. It is also desirable that a fluid, as well as the requisite attributes thereof, be determined for use with the apparatus and method of purifying air which satisfies the electrical and sprayability demands required for use as the spray.
In accordance with a first aspect of the present invention, an apparatus for removing particles from air is disclosed as including at least one inlet for receiving a flow of air, a first chamber in flow communication with the inlet, wherein a charged spray of semi-conducting fluid droplets having a first polarity is introduced to the air flow passing therethrough so that the particles are electrostatically attracted to and retained by the spray droplets, and an outlet in flow communication with the first chamber, wherein the air flow exits the apparatus substantially free of the particles. The first chamber of the apparatus further includes a collecting surface for attracting the spray droplets, a power supply, and a spray nozzle connected to the power supply for receiving fluid, producing the spray droplets therefrom, and charging the spray droplets.
In accordance with a second aspect of the present invention, the apparatus may also include a second chamber in flow communication with the inlet at a first end and the first chamber at a second end, wherein particles entrained in the air flow are charged with a second polarity opposite the first polarity prior to the air flow entering the first chamber. The second chamber of the apparatus further includes a power supply, at least one charge transfer element connected to the power supply for creating an electric field in the second chamber, and a ground element associated with the second chamber for defining and directing the electric field, wherein the air flow pases between the charge transfer element and the ground element.
In accordance with a third aspect of the present invention, the apparatus may further include a fluid recirculation system in flow communication with the first chamber for providing the fluid from the collecting surface to the spray nozzle. The fluid recirculation system includes a device in flow communication with the collecting surface, a reservoir in flow communication with the device, and a pump for providing the fluid to the spray nozzle. The fluid recirculation system may also include a filter positioned between the collecting surface and the pump for removing the particles from the fluid, as well as a device for monitoring the quality of the fluid prior to being pumped to the spray nozzle. A replaceable cartridge may be utilized to house the reservoir, where the cartridge includes an inlet in fluid communication with the collecting surface of the first chamber at a first end and the reservoir at a second end and an outlet in fluid communication with the reservoir at a first end and the pump at a second end.
In accordance with a fourth aspect of the present invention, an apparatus for removing particles from air is disclosed as including at least one defined passage having an inlet and an outlet, wherein each inlet receives a flow of air and the air flow exits the passage at each outlet, and a first area positioned between each inlet and each outlet where a charged spray of semi-conducting fluid droplets having a first polarity is introduced within the passage so that particles entrained within the air flow are electrostatically attracted to and retained by the spray droplets. The apparatus further includes a collecting surface associated with the first area of the passage for attracting the spray droplets, as well as a spray nozzle associated therewith for receiving fluid, producing the spray droplets in the first area of the passage, and charging the spray droplets. The apparatus may also include a second area positioned between the inlet and the first area, wherein particles entrained in the air flow are charged with a second polarity opposite the first polarity. The second area includes at least one charge transfer element associated therewith for creating an electric field in the second area of the passage, as well as a ground element associated therewith for defining and directing the electric field in the second area of the passage.
In accordance with a fifth aspect of the present invention, a method of removing particles from air is disclosed as including the steps of introducing a flow of air having particles entrained therein into a defined area and providing a charged spray of semi-conducting fluid droplets having a first polarity to the defined area, wherein the particles are electrostatically attracted to and retained by the spray droplets, and attracting the spray droplets to a collecting surface. The method further includes the steps of forming the spray droplets from the fluid and charging the spray droplets. The method preferably includes the step of providing a charge to particles in the air flow at a second polarity opposite of the first polarity. The method may further include one or more of the following steps: filtering the air flow for particles having a size greater than a specified size; monitoring quality of the air flow; filtering the particles from the spray droplets; collecting the spray droplets in an aggregate of the fluid; recirculating the fluid aggregate for use in the spray; and, monitoring quality of the recirculated liquid prior to forming the spray.
In accordance with a sixth aspect of the present invention, a cartridge for use with an air purifying apparatus, wherein a charged spray of semi-conducting fluid droplets is introduced to an air flow and collected so as to form a fluid aggregate, is disclosed as including a housing having an inlet and an outlet and a reservoir for retaining the fluid aggregate in flow communication with the inlet at a first end and the outlet at a second end. The cartridge may also include a filter located between the inlet and the reservoir, as well as a pump located between the reservoir and the outlet. The cartridge is configured for the inlet to be in flow communication with the collected fluid aggregate and the outlet to be in flow communication with a device for forming the fluid droplets in the air purifying apparatus. The cartridge housing may function as a collecting surface for the air purifying apparatus and include a spray nozzle associated therewith.
In accordance with a seventh aspect of the present invention, a fluid is disclosed for use as a spray in an air purifying apparatus, wherein particles in an air flow entering the air purifying apparatus are electrostatically attracted to droplets of the spray. The fluid has physical properties which enable a sprayability factor according to a designated algorithm within a specified range, where the sprayability factor is a function of certain physical properties of the fluid which relate to spray droplet size able to be formed and coverage and effectiveness of the spray. Such physical properties of the fluid include flow rate, density, resistivity, surface tension, dielectric constant, and viscosity. The sprayability factor also may be a function of an electric field formed in the air purifying apparatus to which the fluid is introduced. The fluid preferably is semi-conducting, nonaqueous, inert, non-volatile and non-toxic.
These and other objects, features and advantages will become apparent to those of ordinary skill in the art from a reading of the following detailed description and the appended claims. All percentages, ratios and proportions herein are by weight, unless otherwise specified. All temperatures are in degrees Celsius (xc2x0 C.) unless otherwise specified. All documents cited are in relevant part, incorporated herein by reference.